Conventional crawler cranes, such as one disclosed in Document 1 (Japanese Unexamined Patent Publication No. 2006-219241), include: a lower travelling body; an upper slewing body slewably mounted on the lower travelling body via a slewing bearing; an attachment such as boom, jib or the like for lifting a suspended load, the attachment having a proximal end supported on a front portion of the upper slewing body; and a counter weight disposed on a rear portion of the upper slewing body for increasing the lifting capacity. The lower travelling body includes a pair of left and right crawler frames (also referred to as “side frames”) each having an outer periphery on which a crawler is mounted, and a car body (also referred to as “truck frame”) connecting the crawler frames and supporting the upper slewing body.
Such a crawler crane sometimes includes a pair of car body weights (also referred to as “lower weights”) disposed on front and rear sides of the car body of the lower travelling body in order to bring a center of gravity of the entire crawler crane into proximity to a machine center of the crawler crane, as described in the above-mentioned Document 1.